This study presents a method validation for extraction and quantitative analysis of 4-hexylresorcinol residues in shrimp and crab meat using HPLC-FLD. We were focused on the collaboratively analysis of each shrimp and crab meat samples, and developed LC-MS/MS method for the correct confirmation of the identity of compound. Validation parameters; selectivity, linearity, LOD, LOQ, accuracy, precision, and measurement of uncertainty were attained. The measurement of uncertainty was based on the precision study, data related to the performance of the analytical process and quantification of 4-hexylresorcinol. For HPLC-FLD analysis, the recoveries of 4-hexylresorcinol from spiked samples at levels of 0.2-10.0 ppm ranged from 92.54% to 97.67% with RSDs between 0.07% and 1.88%. According to these results, the method has been proven to be appropriate for extraction and determination of 4-hexylresorcinol, and can be used to maintain the safety of shrimp and crab products containing 4-hexylresorcinol residues.

2.Tyrosinase-Catalyzed Hydroxylation of 4-Hexylresorcinol, an Antibrowning and Depigmenting Agent: A Kinetic Study.

4-Hexylresorcinol (HR) is a compound used in the food and cosmetic industries as an antibrowning and lightening agent. Its use is mainly attributed to its inhibitory effect on the enzyme tyrosinase. However, the enzyme hydroxylates HR to an o-diphenol, which it then oxidizes to an o-quinone, which rapidly isomerizes to p-quinone. For tyrosinase to act in this way, the Eox form (oxy-tyrosinase) must be present in the reaction medium, which can be brought about by (a) hydrogen peroxide, (b) ascorbic acid, or (c) catalytic concentrations of o-diphenol and a reductant (NADH) to maintain it constant. This work demonstrates that HR is a substrate of tyrosinase and proposes a mechanism for its action. Its kinetic characterization provides a catalytic constant of 0.85 ± 0.04 s(-1) and a Michaelis constant of 60.31 ± 6.73 μM.

The objective of this study was to demonstrate that a silk fibroin (SF) and 4-hexylresorcinol (4-HR) incorporation membrane could be used for a guided bone regeneration technique. Fourier transform infrared measurements were obtained to determine change of physical property of SF membrane by 4-HR incorporation. Two peri-implant defects, 3.0 × 5.0 mm (width × length), were prepared on the lateral side of the implant hole in the tibia of New Zealand white rabbits (n = 8). The peri-implant defect was left unfilled in the control group. Silk fibroin + 4-HR membrane was applied to the peri-implant defect in the experimental group. The 8 animals were killed at 8 weeks after implantation. Subsequently, removal torque test and histomorphometric evaluation were done. Fourier transform infrared spectroscopy showed no specific chemical interaction between 4-HR and SF. In the histomorphometric analysis, the mean bone regeneration was 18.3 ± 1.9 mm(2) in the experimental group and 9.